steal look, peep at, spy on
覵 centers on covert observation: stealing a look, peeping, or spying on someone or something without being noticed.
覵 combines 閒 (gap, interval) with 見 (see), suggesting looking through a gap or crevice, which fits the meanings of peeping or spying.
The left side 閒 suggests a gap or space between things, and the right side 見 is an eye seeing. Imagine peeking through a narrow gap to steal a look at something hidden.
For カン, picture a spy hiding behind a can, peeping through a gap: can -> カン, and the spy steals a look.